The present invention relates to compressor air bleed valve control apparatus particularly for a gas turbine engine.
It is well known to utilize compressor air bleed valves and control apparatus therefor to vent pressurized air from a multiple stage air compressor to control the air pressures and/or flow therethrough. The bleed valves may be connected to selected stages or all of the stages to control the air pressures thereof by venting the stages simultaneously or by selective venting of the stages depending upon the characteristics of the engine and/or air compressor associated therewith. A compressor such as multiple stage axial flow compressor used in high performance aircraft gas turbine engines requires bleed valve control in response to one or more variable operating conditions which may include flight altitude, engine reverse thrust, engine start, compressor inlet and/or discharge air pressures as well as engine acceleration and deceleration. The desired control over the bleed valves in response to the variable operating conditions may result in control circuitry which increases in complexity in proportion to the number of different operating condition control input signals imposed thereon. Since aircraft control component structure volume and weight must be minimized with no sacrifice in accuracy and/or reliability, it is obvious simple and reliable control elements capable of withstanding engine environment heat and vibration are essential. Furthermore, it is desirable to establish control flexibility whereby the control apparatus may be quickly and easily adjusted and/or modified for use with different engines having correspondingly different engine, including compressor, operational characteristics.